1. Field of the Invention
The present invention relates to a photovoltaic element, and more particularly to a photovoltaic element having a light reflecting layer and made of a non-single crystal semiconductor material containing silicon atoms, for example, amorphous silicon hydride, amorphous silicon germanium hydride, amorphous silicon carbide hydride, crystalline silicon, or polycrystalline silicon. The photovoltaic element of the present invention is suitably applied to a solar cell, a sensor, or an image pick-up device.
2. Related Background Art
Numerous studies on photovoltaic elements have been made from the viewpoints of the material and surface properties of the light reflecting layer.
For example, from the solar cell viewpoint, the reflectivity between amorphous silicon semiconductor hydride (a-Si:H) and metal (Ag, Al, Cu, Cr, Fe, Mo, Ni) has been investigated (A. Madan, M. P. Shaw, The Physics and Applications of Amorphous Semiconductors, Academic Press, 1988). Also a light reflecting layer composed of silver has been examined regarding the relation between reflectivity and texture structure (for example, see "29p-MF-2 Light Confinement Effects On a-SiGe Solar Cell On Stainless Substrate" the 51st Academic Lecture Meeting For The Japan Society of Applied Physics in Autumn 1990, proceedings Vol. 2; "a-SiC/a-Si/a-SiGe Multi-Bandgap Stacked Solar Cells With Bandgap Profiling", Technical Digest of the International PVSEC-5, Kyoto, Japan, 1990, P-IA-15).
Also, textured substrates composed of e.g., Al, SUS/Al/polymer and Ti/Ag/Ti/Al have been examined (M. Hirasaka et. al., "Design Of Textured Al Electrode For A Hydrogenated Amorphous Silicon Solar Cell", in Solar Energy Materials, Vol. 20 (1990) pp. 99-110, North-Holland).
The above-cited conventional photovoltaic elements have excellent photoelectric conversion characteristics, but little examination from the viewpoints of service environment and durability has been made up to now. Hence, from the practical viewpoint, photovoltaic elements having excellent durability and superior characteristics are strongly desired.